Recording stethoscope

ABSTRACT

A recording stethoscope includes a transducer assembly for converting variations in atmospheric or air pressure within the stethoscope into analog electrical signals. The transducer assembly includes a transducer responsive to variations in atmospheric pressure mounted with a housing that includes at least two sections that support the transducer by engaging and clamping the periphery thereof. The variations in atmospheric pressure are intensified by providing a conical chamber in front of the transducer, and the transducer is supported in part by shock absorbing means. A recorder records the output of the transducer, and the recorder is grounded to the chest piece.

[ Nov. 5, 1974' RECORDING STETHOSCOPE [75] Inventors: Earl Slosberg, Cornwell Heights,

Pa.; Samuel D. Williams, Jr., Stratford, NJ.

[73] Assignee: Plastics Development Corporation of America, Philadelphia, Pa.

[22] Filed: Sept. 21, 1972 [21] Appl. No.: 291,101

[52] US. Cl 179/1 ST [51] Int. Cl. H04r 1/46, A61b 7/04 [58] Field of Search 179/1 ST, 107, 156 R;

[56] References Cited UNITED STATES PATENTS l/1935 Flanders 2,902,108 9/1959 Briskier 181/24 3,304,378 2/1967 l-laines et al. 181/24 3,348,535 10/1967 Gregg 179/1 ST 3,455,293 7/1969 Bethune 181/24 RECORDER GROUNDS ?\RECORDER GROUNDS 11/1970 Keesee 179/1 ST 10/1971 Daleiden 179/1 ST Primary Examiner-Kathleen H, Claffy Assistant Examiner-Douglas W. Olms Attorney, Agent, or Firm-Seidel, Gonda & Goldhammer [57] ABSTRACT A recording stethoscope includes a transducer assembly for converting variations in atmospheric or air pressure within the stethoscope into analog electrical signals- The transducer assembly includes a transducer responsive to variations in atmospheric pressure mounted with a housing that includes at least two sections that support the transducer by engaging and clamping the periphery thereof. The variations in atmospheric pressure are intensified by providing a conical chamber in front of the transducer, and the transducer is supported in part by shock absorbing means. A recorder records the output of the transducer, and the recorder is grounded to the chest piece.

5 Claims, 5 Drawing Figures PAIENTEII SIEEI 1 (If 2 \REc0RDER GROUNDS This invention relates to a recording stethoscope. More particularly, this invention relates to a recording stethoscope that includes a transducer assembly for converting variations in atmospheric or air pressure within the stethoscope into analog electrical signals for recording.

A very old technique, useful for inferring the condition of the valves and some of the other internal heart structures, is to listen to the sound that the heart makes as the blood passes through the heart. This is most often done with a stethoscope as many characteristic sounds have long since been identified with characteristic conditions of the heart. Electronic stethoscopes have been available for many years, but they have not gained wide acceptance, perhaps because they offer no particular advantage over the old-fashioned stethoscope which is quite simple and inexpensive.

The present invention relates to a recording stethoscope whereby a doctor can continue to hear the sound that the heart makes as the blood passes through the representing sound wave generated by the stethoscope chest piece. All of this takes place without affecting the sound waves as directly heard by the physician.

It therefore is an object of the present invention to provide a new and improved recording stethoscope for faithfully recording the sounds made by the heart as sound upon play-back is avoided, in the stethoscope of the present invention. ln accordance with the present invention, there is neither mechanical nor electronic distortion of the sound as perceived by the physician.

Faithful electrical recording and reproduction of the sound pressure waves within the stethoscope is made possible in the present invention by providing a highly reliable transducer assembly that is easy to calibrate and manufacture. This is accomplished by a unique de sign of the chamber within which the transducer per se is mounted and by proper mounting apparatus for the transducer.

Existing conventional stethoscopes have, for the most part, a resident peak within their frequency response characteristic that is centered between 5.0 Hz and 200 Hz. Some stethoscopes also have an upper peak centered around l,500 Hz and 3,000 Hz. The primary factors which determine these resident peaks are diaphragm thickness versus mass, and the chest piece chamber volume. These frequency peaks are used to advantage to accentuate certain sounds and physicians are used to hearing them in this manner. The present invention does not alter or'amplify over and above these sounds as they presently. exist within conventional stethoscopes. Rather, the transducer assembly hears the sounds and faithfully converts them into electrical signals that are the same as the sound pressure variations to a high degree of exactness.

In accordance with the present invention, the transducer per se is mounted with a housing that-includes at least two sections which are adjustably joined together. These two sections clamp the transducer into position. In addition, the housing includes a chamber, such as a conical chamber, for amplifying the variations in atmospheric pressure within the stethoscope, such variations blood passes through the heart valves and other parts of that organ.

It is another object of the present invention to provide a recording stethoscope for faithfully recording the sound made by the heart as blood passes through heart valves and other parts of the organ without distrubing the sound as heard directly by a physician.

it is yet another object of the present invention to provide a recording stethoscope which permits the physician to hear the recording exactly as though he were listening directly to a heart.

For the purpose of illustrating the invention, there are shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

F 1G, 1 is a plan view of the recording stethoscope in accordance with the present invention and a recorder.

FIG. 2 is a longitudinal sectional view of the transducer assembly taken along the line 2-2 in FlG. 1.

FIG. 3 is a plan view of a section embodiment of the invention showing a modified transducer assembly.

FIG. 4 is a longitudinal sectional view of the transducer assembly as shown in FlG. 3.

FIG. 5 is a view of a reproduction speaker which may be used in accordance with the present invention.

Referring now to the drawings in detail, wherein like numerals indicate like elements, there is shown in F IG. 1 a recording stethoscope designated generally as 10. The recording stethoscope 10 includes a conventional chest piece 12 designed to pick up the sounds made by blood as it passes through the valves and other internal parts of the heart structure and transfer such sounds into the flexible, hollow conduit 14. The flexible conduit 14 is connected by the Tee 16 to the hollow bran-ch conduits l8 and 20 which in turn are connected to the conventional binaural head piece 22. The hollow Tee connector 24-connects the flexible hollow conduit 14 to a further flexible hollow conduit 26 so that the variations in atmospheric or air pressure within the conduit 14 representing the sounds detected by the chest piece 12 are conducted to the transducer assembly 28 as well as to the binaural head piece 22. The terms atmospheri c pressure or air pressure 'will be used interchangeably in referring to the gaseous medium within the stethoscope. It is noted that the air pressure within the stethoscope is atmospheric pressure modulated by the chest piece 12.

The flexible hollow conduits 14, 18, 20 and 26 may be made of any conventional material ordinarily used in stethoscopes. However, in a preferred embodiment, the flexible, hollow conduits l4 and 26 as well as the Tee connector 24 are made to be conductive either by impregnating the same with a conductive material or by passing flexible conductors through the walls thereof.

For example, conventional grounding cable may be.

used for this purpose. In alike manner, the transducer assembly 28 is connected by a grounding cable or similar conductor to the recording machine 30 along the cable 32. This in effect connects the chest piece 12 I physician. The use of a floating ground effected as herein described compensates for variations in the electrostatic potential voltage of the patients body which varies considerably depending upon such conditions as temperature, humidity, floor covering, fluorescent or incandescent lighting, operating electrical machinery in the examining room, and other factors. Such variations in electrostatic voltage potential can effect the fidelity of the recording unless compensated for. The use of a floating ground as described accomplishes this.

The recording machine 30 is a magnetic tape deck including appropriate detectors, amplifiers, filters and the like whose frequency response is properly adjusted to accurately record the electrical signals transduced by the transducer 34 mounted within the transducer assembly 28.

As best shown in FIG. 2, the transducer 34 is mounted within the housing 36 which comprises a first section 38 and a second section 40 telescopically joined together by means of the screw threads 42.

The first section 38 is formed so as to provide annular shoulder 44 at the end of chamber 46 defined by conical wall 48. Second section 40 is constructed so as to provide annular shoulder 50 positioned in opposed relation to annular shoulder 44 when the two sections are assembled together.

Opposed annular shoulders 44 and 50 clamp the periphery of transducer 34 between them. Shock absorbing means in the form of O-ring S2 and 54 are positioned between the shoulders 44 and 50 and are the material that actually engages the shoulders and the transducer 34. The shock absorbing means 52 and 54 act as mechanical vibration and shock dampeners, and they also function as hinges supporting the transducer 34 as it vibrates back and forth in response to the variations in atmospheric pressure incident upon it from the chest piece 12. It should be noted that the transducer 34 does not touch any part of the housing 36 including the first section 38 and the second section 40. Rather, it is suspended entirely by the compression of the rings 52 and 54 between the first section 38 and second section 40. The screw threads 42 provide a means for adjusting the amount of such compression and hence permits a means whereby the transducer 34 can be calibrated by entering calibrated air pressure pulses into the stethoscope and varying the amount of compression while observing the output of the transducer 34 on an electrical measuring instrument such as an oscilloscope.

Upon achieving the proper amount of compression, the first section 38 and second section 40 are locked in position by means of the set screw 56 or any other conventional locking means. It should be understood that the screw threads 42 are an example of one means for adjusting the amount of compression upon the periphery of the transducer 34 to lock it in position. Other means for fitting the first section38 and second section together in compression to thereby clamp the transducer 34 in position may be provided as desired.

The edge of the transducer 34 as well as the outermost surface of the O-rings 52 and 54 is wrapped in insulating tape 55 which preferably is coated with polytetraflouroethylene or its equivalent. Such tape provides insulation for the outer edge of the transducer 34 while at the same time allowing free flexure thereof.

The electrical conductors 60 for the transducer 34 are brought out to the cable 32 and held in position by the bracket 62 fixed to the second section 40 by means of the threaded fastener 64. The cable 32, which preferably is a braided coaxial cable, conducts the output of the transducer 34 to the recording machine to which it is connected by means of the jack 66.

The transducer 34 is preferably a barium titanate piezoelectric disc which generates a voltage when it is flexed. By way of example but not limitation, the trans ducer 34 may be a Bimorph disc such as is manufac tured by the Vernitron Division of Clevite, Bedford, Ohio. Those skilled in the art will readily recognize that other, equivalent transducers may be substituted for the transducer 34 as described above.

As previously indicated, the chamber 46 is frustoconical as defined by the conical wall 48. The transducer 34 is positioned adjacent the large opening in the chamber 46 and the small opening is in open connec-- tion with the flexible, hollow conduit 26 through the neck 68. The frusto-conical shape inside the'cham ber 46 reinforces the variations in atmospheric pressure generated by the chest piece 12 to provide greater pressure upon the surface of transducer 34. e

The physician puts the stethoscope 10 in use by connecting the cable 32 to the recording machine 34 through the jack 66. The recording machine is put in operation and the physician thereafter commences his examination in the ordinary manner. Thus, he follows a routine procedure of examination at all times listening to the movements of the heart with his professionally trained ear. He hears the heart exactly as he has always heard it through the binaural head piece 22. Simultaneously, what he is hearing is transduced into electrical signals within the transducer assembly 28 and recorded in the recording machine 30 exactly as he hears it. Thus, the physician can playback what he has heard at any time in the future for further diagnosis or to compare past conditions with present conditions.

So that there is no distortion of the sounds that the physician hears upon playback, this is accomplished using the speaker assembly illustrated in FIG. 5. The physician places the recording machine 30 in its playback mode and connects the speaker assembly 70 thereto through jack 72. The output of the playback channel of the recording machine is conducted through cable 74 to the speaker 76 which transduces the electrical signals into acoustic signals. The speaker 76 may be, by way of example, a Telethin speaker manufactured by the Telex Acoustic Products Division of Telex Corporation. The output sound signals of the speaker 76 are emitted through the hollow conduit 78 in the form of variations in atmosphericpressure. These signals are coupled into the stethoscope 10 by removing the transducer assembly from connection with the flexible conduit tube 26 and inserting the conduit 78 in its place. Thus, the sound is returned to the stethoscope as before in exactly the same manner as it left.

Referring now to'FlGS. 3 and 4, there is shown another embodiment of the present invention wherein the Tee connector 24 is removed and a modified trans ducer assembly housing 80 is put in its place. With respect to the embodiment illustrated in FIGS. 3 and 4, only the transducer assembly is illustrated since the remainder of the stethoscope remains unchanged.

As shown, the flexible hollow conduit 14 is connected to both an entrance port 82 and an exit port 84 of the first section 86 which together with the second section 88 forms the transducer assembly housing 80.

The transducer 34 is held in position between the first section 86 and the second second section 88 in the same manner that the transducer 34 is clamped in position in the embodiment illustrated in FIG. 2. For this reason, like elements illustrated in FIGS. 3 and 4 bear the same numeral except that it is primed. Thus, the embodiment of FIGS. 3 and 4 includes the shock absorbing O-rings 52' and 54 and the edge of the transducer 34' is wrapped in polytetraflouroethylene tape 55'.

The first section 86 is telescopically positioned within the second section 88 by means of the screw threads 90 and they are locked in position by means of the set screw 92. Clamping pressure is applied to the O-rings 52' and 54 between which the transducer 34' is positioned by the annular shoulders 94 and 96. As in the embodiment illustrated in FIG. 2, the correct amount of clamping force is adjusted by applying a calibrated pressure signal to the chest piece.

The electrical signal generated by the transducer 34 is brought out through conductors 60' which are con nected to the cable 32' fixed in position within the opening in the second section 88- by means of the bracket 98. Bracket 98 is threadedly fixed to the second section 88 by threaded fastener 100.

The interior of first section 86 includes the frustoconical chamber 102 defined by the conical wall 104. The small end of the chamber 102 opens directly into the tubing 14' while the large end is adjacent to the transducer 34'. The conical chamber 102 serves to increase the pressure variations produced by the chest piece as they are received from the flexible conduit 14. The transducer assembly illustrated in FIGS. 3 and 4 functions and is used in thesame manner as described with respect to the transducer assembly illustrated in FIG. 2.

By way of example, a chamber 102 which provides good amplification of the variations in atmospheric pressure within the first section 86 has a conical wall 104 at an angle of approximately 41 with respect to an imaginary straight line extending parallel to the conduit 14'. The depth of the chamber 102 from its small opening to its large opening is approximately .324 inches. The diameter of the small opening is approximately .099 inches and the diameter of the large opening of the chamber 102 is approximately .840 inches. The

transducer 34' is nominally .050 inches from the large opening of the chamber 102. This latter dimension is adjusted according to the calibration of the recording stethoscope as described above.

The present invention may be embodied in other spe cific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

We claim: 7

l. A recording stethoscope, comprising:

stethoscope means including an electrically conductive chest piece;

a transducer assembly for converting variations in air pressure within said stethoscope means into analog electrical signals for recording, said transducer assembly comprising a two section housing and means for adjustably connecting said two sections together, at least a part of said housing being electrically conductive, a disc shaped transducer responsive to variations in air pressure to generate the analog electrical signals, said transducer being mounted within said housing and being clamped at its periphery between said two sections, a resilient annular member positioned on each side of said transducer between said transducer and each of said two housing sections, an opening in said housing in open communication with the interior of said stethoscope means, and air pressure intensifying means in the form of a conical chamber between said opening and said transducer for amplifying variations in air pressure, said opening being at the smaller end of said conical chamber and said disc shaped transducer being at the larger end;

an electrically conductive hollow conduit connecting said chest piece and said opening of said transducer assembly; and an electrical connection means adapted for connection of the output of said transducer to a recording means, said electrical connection means including a conductor for connecting the conductive portion of said transducer assembly housing to the ground or reference potential connection of said recording means whereby the ground or reference potential of the recording means is the same as the potential of the transducer assembly housing and the chest piece adapted to be in contact with a subject being examined.

2. A recording stethoscope in accordance with claim 1 wherein said electrically conductive hollow conduit is a flexible conduit comprised of material impregnated with a conductive material.

3. A recording stethoscope in accordance with claim 1 wherein said electrically conductive hollow conduit.

is comprised of a flexible conduit having a flexible electrical conductor within the wall of the conduit.

4. A recording stethoscope in accordance with claim 1 including a speaker assembly for transducing recorded electrical signals into analog sound signals, and means to interchangeably couple said speaker assembly and said transducer assembly to said stethoscope.

5. A recording stethoscope in accordance with claim 1 wherein said transducer assembly is mounted directly on a hollow conduit connecting the chest piece and a set of ear pieces of said stethoscope means, said opening in said housing of said transducer assembly being in open communication with the inside of said conduit, said conical chamber having an axis perpendicular to the center line of the conduit connecting said chest piece and said set of ear pieces. 

1. A recording stethoscope, comprising: stethoscope means including an electrically conductive chest piece; a transducer assembly for converting variations in air pressure within said stethoscope means into analog electrical signals for recording, said transducer assembly comprising a two section housing and means for adjustably connecting said two sections together, at least a part of said housing being electrically conductive, a disc shaped transducer responsive to variations in air pressure to generate the analog electrical signals, said transducer being mounted within said housing and being clamped at its periphery between said two sections, a resilient annular member positioned on each side of said transducer between said transducer and each of said two housing sections, an opening in said housing in open communication with the interior of said stethoscope means, and air pressure intensifying means in the form of a conical chamber between said opening and said transducer for amplifying variations in air pressure, said opening being at the smaller end of said conical chamber and said disc shaped transducer being at the larger end; an electrically conductive hollow conduit connecting said chest piece and said opening of said transducer assembly; and an electrical connection means adapted for connection of the output of said transducer to a recording means, said electrical connection means including a coNductor for connecting the conductive portion of said transducer assembly housing to the ground or reference potential connection of said recording means whereby the ground or reference potential of the recording means is the same as the potential of the transducer assembly housing and the chest piece adapted to be in contact with a subject being examined.
 2. A recording stethoscope in accordance with claim 1 wherein said electrically conductive hollow conduit is a flexible conduit comprised of material impregnated with a conductive material.
 3. A recording stethoscope in accordance with claim 1 wherein said electrically conductive hollow conduit is comprised of a flexible conduit having a flexible electrical conductor within the wall of the conduit.
 4. A recording stethoscope in accordance with claim 1 including a speaker assembly for transducing recorded electrical signals into analog sound signals, and means to interchangeably couple said speaker assembly and said transducer assembly to said stethoscope.
 5. A recording stethoscope in accordance with claim 1 wherein said transducer assembly is mounted directly on a hollow conduit connecting the chest piece and a set of ear pieces of said stethoscope means, said opening in said housing of said transducer assembly being in open communication with the inside of said conduit, said conical chamber having an axis perpendicular to the center line of the conduit connecting said chest piece and said set of ear pieces. 